Table of Contents

Venting/pumping Intermediate Image box and filling PPACs with gas

The procedures to vent/pump the S800 Intermediate Image box, and/or filling the PPAC detectors with gas must be done carefully to ensure that the PPACs are not damaged. For instance, before venting the chamber, we have to make sure that the PPACs are empty and equalized with respect to the vacuum in the chamber. In order to avoid errors, an automated gas handling system (II-GHS) was designed to perform these tasks safely. The system is schematically illustrated in the figure below. It shows the status of the valves (red: closed, white: open) when the intermediate image chamber is under vacuum and the PPACs are filled with gas:

The II-GHS equipment (valves, flow-meter, pipes, isobutane gas bottle. etc.) are located on the west balcony of the top level in the S3 vault (see figure below):

Vent Intermediate-image chamber

Requirements: PanelMate files S3_Gas_Handling and S800Vac

Verify that PPACs are in automatic mode with gas removed (S3_Gas_Handling)

The “GH System Status box should read “Auto Mode Gas Removed”

If gas is removed but the system is not in the automatic mode, consult the Beam Physicists or Device Physicist. NOTE: the only valves that should be open in S3_Gas_Handling are the “Det Bypass” and “Chmbr Bypass

The status in the box “VENT STATUS” should change from “WAITING FOR VENT TIMER” to “VENT PROCEDURE STOPPED”

You can now open the chamber

Pumping Intermediate-image chamber

Requirements: PanelMate files S3_Gas_Handling and S800Vac

Verify that Chamber is closed and pressure-relief valve (north side of the chamber) is properly closed (NOTE: sometimes, due to overpressure from dry N2 during the venting procedure, the O-ring in pressure-relief valve flange is moved out of place)

Check “PUMPDOWN STATUS INTERMEDIATE IMAGE BOX”; it should read “PUMPDOWN STOPPED”. Select that box and click on “START PUMPDOWN”. The chamber will not be pumped yet because the manual roughing pump valve is closed.

Slowly crack manual roughing valve

Start slow (< 1 Torr/sec). Chamber pressure is displayed in I215PG in S800Vac PanelMate. There is also a local display of the mechanical pump pressure on a Granville-Phillips 275 Mini-Convectron, which is helpful to control rate of pumping.

Verify PPACs changing shape through sighting window.

Pump to about 100 Torr before fully opening the roughing valve.

Once roughing valve is fully open, retract PPACs and turn lights off.

When the pressure in I215PG is below 200 mTorr, the Turbo Pump will start automatically through the following sequence:

I214RV will be closed

I214FV will be opened

I214GV will be opened

When the pressure ready by I215PG is few mTorr, you can turn on the ion gauge I213IG. Good vacuum will take ~1-2 hours.

NOTE: it sometimes happens that the foreline pressure rises above the trip point for the Turbo Pump (e.g. if the pumpdown timer expires before pressure is below 300 mTorr). In this case the foreline valve needs to be bypassed open (in PanelMate) and the TP needs to be restarted.